1. Field of the Invention
This invention relates generally to medical appliances; and more particularly to a phlebotomy set for withdrawing liquids -- usually blood -- from a patient's body.
2. Prior Art
As is well known, there are myriad very important medical uses for withdrawing blood and other liquids from patients. It is also known that a severe problem has developed in relation to all such devices.
That problem arises from the continuing presence of horrible diseases, particularly fatal and currently incurable diseases such as acquired immune deficiency syndrome ("AIDS") and hepatitis, that are transmitted by exchange of body substances between people. These diseases have led medical institutions to exclusively use disposable needles for both injection and withdrawal of liquids from patients.
A severe residual risk remains, however, for medical personnel themselves in the inadvertent touching of needle tips after withdrawal from infected patients. Medical needles are designed and manufactured specifically to be extremely sharp and to puncture skin and flesh with only the slightest pressure.
As a result, what would ordinarily be an inconsequential scratch or pinprick can bring and has brought severe disease or even death to many medical staff members and others. Needless to say, health-care professionals are well aware of this risk and take considerable precautions to avoid such inadvertent punctures; thus the risk is reduced on a "probability" basis to an exceedingly small value.
Nevertheless, the exposure is so massive for working doctors, nurses and technicians that occasional punctures are inevitable. As a practical matter, it is virtually impossible for such an individual to reduce the incidence of accidental puncture to less than, say, one every year or perhaps one every few years.
Of course, not every such puncture follows contamination of the needle by a patient carrying a transmissible fatal disease. Nevertheless, there are enough medical personnel and enough such patients that a significant number of medical staffers die -- and of course a greater number become very sick -- from these accidents.
In discussion of this problem, needles of the types used with syringes commonly come to prominence. Though the word "hypodermic" has somewhat passed out of current usage in the medical profession, I shall for purposes of definiteness and simplicity refer to needles used with syringes for giving injections as "hypodermic needles." Needles used in drawing blood will be called "phlebotomy needles." By this terminology I mean to clearly distinguish all such needles from needles that are used for cannula insertion, the specific subject matter of my previously mentioned issued patent.
As detailed in that patent, the actual manual manipulations involved in using hypodermic and phlebotomy needles -- as compared with cannula-insertion needles -- are relatively favorable to avoiding puncture accidents. For that reason my first concern was for improvement of cannula-insertion needles.
The dangers of infection with hypodermic and phlebotomy needles nevertheless remain very important, partly because they are used in such enormous quantity. As noted in my patent, I did not mean to imply that hypodermic and phlebotomy needles are safe. There is an important potential for inadvertent unsheathing and many other kinds of accidents.
For example, as mentioned in my patent there are learning situations and emergencies, and circumstances in which the usual manual manipulations are complicated by patient mental or physical condition. While these situations are only a fraction of all instances of use of hypodermic and phlebotomy needles, this fraction nonetheless represents an enormous number of individual occurrences.
In a present-day standard, commercially available phlebotomy device -- sometimes termed a "phlebotomy set" -- the needle is stainless steel, hollow, and extremely sharp at its frontal end. The needle shank is threaded by the user onto a hollow handle, and more particularly to a transverse front end wall of the handle. The sharp end of the needle projects forward from the handle, and the rear end of the needle projects rearward into the interior of the handle.
The handle is generally a molded plastic cylinder, typically made of polycarbonate, open at the rear. The open rear portion of the handle forms a skirt that guards against casual contact with the rear end of the needle.
After assembly of the needle and handle, blood is collected in a separate liquid-receiving device, which usually takes one of two conventional forms. One such liquid-receiving unit is a remote receptacle, operated at a reduced internal pressure.
This remote receptacle communicates with the collection needle through a liquid-conveying long flexible tube, which is inserted through the open rear skirt of the handle and attached to the rear end of the needle. In a phlebotomy set designed for use with this type of receptacle, the rear end of the needle is cut off at right angles and given a smooth finish -- to facilitate pushing the collection tube into place over the rear end of the needle.
With a remote receptacle, the sequence of procedural steps is somewhat variable. In principle the receptacle may be depressurized and the tubing connection completed before or after the system is connected to the patient's body.
In any case the sharp forward end of the needle is inserted into the patient's blood vessel -- or in some cases possibly into a body cavity, or an abscess, or wherever fluid communication is to be established. The liquid to be collected flows through the needle and tubing into the remote receptacle, impelled by the difference between the blood pressure or other liquid pressure within the patient's body and the low pressure in the receptacle.
Another type of liquid-receiving unit known in present medical use is a vial that is sealed at a forward end by a piercable elastomeric wall or stopper. The vial is supplied at a reduced internal pressure.
In a phlebotomy set designed for use with this type of receptacle, the rearward end of the needle as well as the forward end is sharpened. In use, the sharp forward end of the collection needle is first inserted into position in the patient's body, and then the piercable wall of the collection vial is impaled on the sharp rear end of the collection needle. The liquid being collected flows into the evacuated vial under the influence of the pressure differential beween the liquid pressure within the patient's body and the pressure in the vial.
Phlebotomy devices for use with evacuated vials present a unique additional hazard -- namely, the possibility of puncture at the sharp rear end of the needle. Since this end too carries the patient's possibly contaminated blood or other body fluid, all of the same dangers of infection mentioned earlier are operative here.
Typically a separate safety cover is supplied in place on at least the forward sharp end of the needle. The separate safety cover firmly grips the transverse wall of the handle, or a hub structure on the needle itself, and entirely covers the segment of the needle on one side of the tranverse wall.
This guarding prevents accidental puncture and accidental contamination of the needle by substances in the environment, before use. To use the needle, the safety cover must be entirely removed and set aside.
As already suggested, our focus of concern now shifts to the possibility that the needle may be contaminated by substances in the patient, during use. Accordingly the safety cover is to be replaced over the sharp end of the needle to prevent accidental puncture and particularly to prevent contact of people, other than the patient, with possible contaminants on the needle.
It is here that the prior art fails to be effective, since the process of replacing the safety cover -- and in vacuum-vial devices two safety covers -- is subject to many risks of inadvertent mishandling as previously mentioned.
The medical marketplace has seen various appliances and apparatuses aimed at solving these problems. One such device is a special form of hypodermic needle, available commercially from the firm ICU Medical, Inc. under the trade name "ICU High Risk Needle." The ICU device is fitted with a sliding sheath that is carried on the shaft of the hypodermic needle itself. After use the sheath is advanced forward over the needle tip.
That device undoubtedly serves a useful purpose, and could be adapted for use on phlebotomy-set needles. It is certainly not my desire to criticize what is apparently the only commercial effort directed to an important problem.
On the other hand, that device evidently has limitations that should be mentioned. First, the ICU High Risk Needle is offered as a special item at a special price, for use only with patients known to be "high risk" patients. Not all patients carrying transmissible fatal diseases are known to be high risks.
Secondly, the sheath is attached halfway out the needle, where there would appear to be potential for inadvertent application of lateral force with sufficient leverage to snap off the needle. If that should occur before the sheath were fully advanced, the potential for accidental puncture could be substantial.
Thirdly, it is not clear that the sheath when advanced locks in place firmly enough to withstand normal jarring in the workplace. It thus offers very limited protection.
Fourthly, an evacuated-vial phlebotomy set would require more than one sheath. That is, one would be required for each of the two sharp ends -- doubling both the cost of manufacture and the attention required by medical personnel to secure the device after use. Furthermore, reaching into the rear skirt to advance the sheath could itself be a hazardous procedure.
Fifthly and finally, the ICU needle is necessarily more than twice as long as a standard needle.
A number of patents have been issued for devices that shield medical needles. Among these is U.S. Pat. No. 4,592,744, issued June 3, 1986, to Janine C. Jagger et al. This patent illustrates and describes a device that facilitates retraction of a phlebotomy needle into a personnel-protective enclosure -- which also serves as a handle for the device. The Jagger patent also shows and describes another device that similarly facilitates retraction of a hypodermic needle. In both of these devices the retraction procedure is relatively cumbersome.
In the Jagger phlebotomy device, which is of the evacuated-vial type, the final vial is used as a tool to unscrew the needle from a transverse wall at the forward end of the handle. This is done while the needle still pierces -- and may damage -- the elastomeric stopper.
To permit this unthreading, the vial carries a special dual boss at its forward end, adjacent to the piercable the stopper. When properly positioned by a user, the dual boss engages a mating structure on the rear end of the needle hub, for unscrewing the needle from the handle.
Then the user pulls the vial, with its blood sample, rearward out of the handle. As the receptacle is withdrawn, the loosened needle comes with it, since the needle is still engaged with the stopper.
The needle moves rearward until the sharp forward point passes through the threaded hole in the transverse wall. With further rearward motion the needle is then trapped by its flange in the handle, allowing the collection vial and stopper to be separated from the needle. A separate rear cap is (or at least should be) applied over the rear skirt of the handle, to guard the sharp rear end of the needle.
In the Jagger hypodermic device, the needle is mounted by a relatively tight press fit to the forward end of a syringe that is fitted within the handle. The needle also extends in a relatively loose press fit through a hole in the front of the handle.
After use, the entire syringe must be pulled bodily out of the back end of the handle, carrying the needle rearward out of its front-end press fit with the handle, and into the cavity within the handle. The needle is carried in a flange that is too wide to escape from the rear end of the handle, and accordingly is pulled away from its tight press fit at the front end of the syringe.
The needle is thus trapped within the handle. The user must then dispose of the handle (with enclosed needle) and syringe separately.
The two forms of the Jagger invention -- both the phlebotomy device and the hypodermic device -- are undesirable in their arrangements for arming the apparatuses for retraction of the needle. By "arming" I refer to a process of discriminating between (1) operation of the device, for drawing blood or loading a syringe before injection; and (2) retraction of the needle, for disposal
Phlebotomy-device operation includes moving each vacuum vial rearward and outward after it is full. Syringe operation includes filling the syringe, by pulling rearward and outward on the plunger, either in drawing blood or prior to an injection.
Thus, in Jagger's phlebotomy device and syringe alike, operation necessarily involves rearward motion of some kind. Retraction of course also involves rearward motion.
The apparatus must somehow be made so that it will not retract the needle during operation, but will retract the needle after operation. Jagger uses two different arming philosophies in her two different devices.
The two philosophies actually are opposite, and as a result have opposite drawbacks. Both sets of drawbacks, however, are severe.
I shall first consider the Jagger phlebotomy needle. Here an arming step is required, and the required step is unduly cumbersome.
As mentioned above, a user must unscrew the flange of the phlebotomy needle -- using the last vacuum vial as a driver -- before pulling the flange and needle back into the handle. This arrangement for retraction is likely to be bothersome to busy medical personnel, and therefore even more adverse to reliable, safe operation.
Now I shall turn to the Jagger hypodermic needle. In that device, proper syringe operation and proper retraction thereafter both depend upon maintenance of the design relationships between two friction-and-force relationships.
To fill the syringe a user must first advance the plunger fully forward, insert the needle tip into the liquid to be loaded, and then pull the plunger back. In pulling the plunger back, the user will most naturally grasp the outer handle or enclosure.
Thus the user relies upon relatively high friction between the needle-carrying nosepiece and the front end of the handle to keep the assembly together during loading. Later, however, the user relies upon relatively low friction between those same two parts to break the assembly down for needle retraction and disposal.
In essence, the device is supposed to be self-arming for retraction. The user does nothing to prepare for needle retraction after use, but rather depends upon two friction/force relationships to discriminate between loading and retraction.
These relationships, however, are too easily upset. For example, they can be disturbed by temperature variations, leakage of slippery or sticky substances, or improper insertion of the syringe tip into its mating receptacle at the rear of the needle flange.
In such circumstances the syringe can be extracted from the needle flange before the needle is retracted -- leaving no proper means for retraction. Conversely, the syringe can be held too tightly in place in the handle, requiring separation by force -- and so leading to accidental punctures, thereby defeating the purpose of the safety device.
All of this is a natural result of Jagger's syringe design, which attempts to avoid the necessity for a physical arming step on the part of the user. In effect Jagger's patent illustrates two opposing philosophies for retraction arming. One may be said to represent an excessive arming step, and the other an inadequate arming step. Both, however, tend toward the same result -- a relatively ineffective device.
Other prior patents describe devices for automatic or semiautomatic resheathing of hypodermic syringes.
U.S. Pat. No. 4,026,287 to Haller is among the better of these, since it at least provides for retraction of the used needle into a cavity in a unitary, sturdy structure. The Haller device, however, requires screwing the syringe plunger into the back of the needle flange after use, to destroy a frangible seal around the flange and then retract the needle.
Haller, like Jagger, thus imposes an undue procedural burden on the user. Considered objectively, the amount of effort required to unthread the needle from the handle may be small; however, in this regard it is important to bear in mind a crucial psychological aspect of safety devices:
The additional procedure of unthreading the needle from its mount does not further any medical procedure which the user is assigned to perform, but only substitutes for placing a safety cap carefully over the needle. Consequently if personnel perceive the unthreading step required to make use of a particular safety feature as unduly burdensome, they simply will not use the safety features of the device at all.
If that happens regularly, then of course not only does the hazard persist but in addition the entire cost of the safety features is wasted. Seen in this light, the relatively small amount of effort involved in unthreading the needle is more correctly seen as a factor that controls the overall utility of the device.
Haller also fails to protect against inadvertent insertion of fingertips into the syringe barrel. U.S. Pat. No. 4,631,057 to Mitchell also leaves the needle accessible to fingertips through the unsealed forward end of the sheath.
Another patented device providing better frontal shielding against fingertip insertion in a vacuum-vial phlebotomy set is disclosed in U.S. Pat. No. 4,643,199 of Jennings, Jr. et al. That device has an auxiliary inner barrel, within the needle-holder handle, that is manipulated to retract the needle into the handle and lock it there.
The necessary manipulation involved is perhaps slightly less involved than in the Jagger device, but yet does include three separate motions: first a rotation (in a particular direction), then an axial telescoping motion, and finally another rotation (in the same particular direction). Furthermore an additional fourth separate motion is required to complete the task: locking a safety cap over the rear end of the auxiliary barrel.
Still other patented devices that provide good frontal shielding against fingertip insertion, but are otherwise remote from phlebotomy concerns, are U.S. Pat. Nos. 4,573,976 (Sampson) and 4,643,200 (Jennings, Jr.).
Worthy of mention for its provision of positive resistance to jarring of a syringe needle out of retracted position is U.S. Pat. No. 4,425,120 to Sampson et al. That device pays for its effective safety locking with complexity of the manual manipulations required in use. Similar observations apply to U.S. Pat. No. 3,890,97l to Leeson.
Numerous devices for providing merely visual shielding or screening of hypodermic syringes have been patented. Among these are U.S. Pat. Nos. 2,876,77O (White), 2,674,246 (Bower) and 3,134,380 (Armao). Such devices are actually counterproductive with respect to present purposes, since they effectively conceal the presence of a dangerously sharp and possibly contaminated needle.
Thus the prior art has failed to provide an optimum safety device for use under modern conditions in the field of the present invention. No prior-art device provides the necessary sure and easy operation that is essential to the effectiveness of such protection.